[PATCH v1] mm: Remove arch_flush_tlb_batched_pending() arch helper

[Ryan Roberts]

Since commit 4b634918384c ("arm64/mm: Close theoretical race where stale
TLB entry remains valid"), all arches that use tlbbatch for reclaim
(arm64, riscv, x86) implement arch_flush_tlb_batched_pending() with a
flush_tlb_mm().

So let's simplify by removing the unnecessary abstraction and doing the
flush_tlb_mm() directly in flush_tlb_batched_pending(). This effectively
reverts commit db6c1f6f236d ("mm/tlbbatch: introduce
arch_flush_tlb_batched_pending()").

Suggested-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
---
 arch/arm64/include/asm/tlbflush.h | 11 -----------
 arch/riscv/include/asm/tlbflush.h |  1 -
 arch/riscv/mm/tlbflush.c          |  5 -----
 arch/x86/include/asm/tlbflush.h   |  5 -----
 mm/rmap.c                         |  2 +-
 5 files changed, 1 insertion(+), 23 deletions(-)

diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index aa9efee17277..18a5dc0c9a54 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -322,17 +322,6 @@ static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm)
 	return true;
 }

-/*
- * If mprotect/munmap/etc occurs during TLB batched flushing, we need to ensure
- * all the previously issued TLBIs targeting mm have completed. But since we
- * can be executing on a remote CPU, a DSB cannot guarantee this like it can
- * for arch_tlbbatch_flush(). Our only option is to flush the entire mm.
- */
-static inline void arch_flush_tlb_batched_pending(struct mm_struct *mm)
-{
-	flush_tlb_mm(mm);
-}
-
 /*
  * To support TLB batched flush for multiple pages unmapping, we only send
  * the TLBI for each page in arch_tlbbatch_add_pending() and wait for the
diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index 1a20dd746a49..eed0abc40514 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -63,7 +63,6 @@ void flush_pud_tlb_range(struct vm_area_struct *vma, unsigned long start,
 bool arch_tlbbatch_should_defer(struct mm_struct *mm);
 void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch,
 		struct mm_struct *mm, unsigned long start, unsigned long end);
-void arch_flush_tlb_batched_pending(struct mm_struct *mm);
 void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);

 extern unsigned long tlb_flush_all_threshold;
diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
index e737ba7949b1..8404530ec00f 100644
--- a/arch/riscv/mm/tlbflush.c
+++ b/arch/riscv/mm/tlbflush.c
@@ -234,11 +234,6 @@ void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch,
 	mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
 }

-void arch_flush_tlb_batched_pending(struct mm_struct *mm)
-{
-	flush_tlb_mm(mm);
-}
-
 void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
 {
 	__flush_tlb_range(NULL, &batch->cpumask,
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index e9b81876ebe4..00daedfefc1b 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -356,11 +356,6 @@ static inline void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *b
 	mmu_notifier_arch_invalidate_secondary_tlbs(mm, 0, -1UL);
 }

-static inline void arch_flush_tlb_batched_pending(struct mm_struct *mm)
-{
-	flush_tlb_mm(mm);
-}
-
 extern void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);

 static inline bool pte_flags_need_flush(unsigned long oldflags,
diff --git a/mm/rmap.c b/mm/rmap.c
index fb63d9256f09..fd160ddaa980 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -746,7 +746,7 @@ void flush_tlb_batched_pending(struct mm_struct *mm)
 	int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;

 	if (pending != flushed) {
-		arch_flush_tlb_batched_pending(mm);
+		flush_tlb_mm(mm);
 		/*
 		 * If the new TLB flushing is pending during flushing, leave
 		 * mm->tlb_flush_batched as is, to avoid losing flushing.
--
2.43.0